Radiator caps are used to perform a critical function in the cooling system operation of a motor vehicle. They are used to seal a filler opening needed for filling or topping off a cooling system liquid. The cooling liquid s used inside a vehicle's heat exchange system, (radiator) and assist in keeping a vehicle's engine temperature stabile and operating at a safe and constant temperature. As this liquid is heated by vehicle's engine, pressure from liquid expansion occurs. Most radiator caps are designed to not only provide a primary and secondary water tight seal but also acts a pressure relief valve. Radiator cap construction generally incorporates a main spring having a rated collapse pressure allowing it to release pressure from the secondary seal to the atmosphere or to an over flow system. Improper radiator cap operating pressures, either too high or too low, with in the system can cause internal damage to the vehicle's engine, radiator or cause overheating problems due to cooling liquid loss.
It is recommended by not only vehicle manufacturers but the radiator cap and radiator manufactures to have radiator caps tested at certain intervals to check the integrity of its pressure relief and sealing capabilities. Radiator cap testing requires a technician to have testing equipment which generally consists of a mechanical hand pump and a series of adapters that simulate radiator filler necks. The technician installs the radiator cap and connects the hand pump to the correct filler neck adapter. The technician then hand pumps air pressure to the sealed adapter while having to watch a pressure gauge to test sealing integrity and how many pounds pressure the radiator cap will hold before it relieves pressure. This process is awkward and time consuming for the technician to perform.